Light-receiving module and light-receiving device having malfunction preventing structure

ABSTRACT

A light-receiving device has a high-concentration impurity layer of a first conductivity type and a high-concentration impurity layer of a second conductivity type surrounding it formed on a substrate of the first conductivity type having a low impurity concentration so as to function as a light-receiving portion. The high-concentration impurity layers of the first and second conductivity types are arranged in the same direction as the top surface of the substrate. A layer having a short carrier life time is formed on the bottom surface of the substrate. Thus, carriers ascribable to unnecessary light components that have reached the layer having a short carrier life time have a shorter life time, making it possible to sufficiently cut unnecessary long-wavelength light components.

TECHNICAL FIELD

The present invention relates to a light-receiving device and to alight-receiving module incorporating it.

BACKGROUND ART

A light-receiving device incorporated in a light-receiving module forremote control applications is generally composed of a light-receivingdevice for infrared light. Conventionally known examples of suchlight-receiving devices are those having a light-receiving portioncomposed of a PIN-type diode formed in the thickness direction of asubstrate as shown in FIG. 9 or along the surface of a substrate asshown in FIG. 10. In FIG. 9, reference numeral 101 represents a P−layer, reference numeral 102 represents a P+ layer, reference numeral103 represents an N+ layer, reference numeral 104 represents aninsulating layer of SiO₂, reference numeral 105 represents an Nelectrode, and reference numeral 106 represents a P electrode. Thestructure shown in FIG. 9 has the disadvantage that carriers 107ascribable to long-wavelength light components that have reached the P+layer 102 diffuse (indicated by arrow Lp) and produce a photoelectriccurrent. On the other hand, in FIG. 10, reference numeral 201 representsa depletion layer (of which the thickness is represented by W),reference numeral 202 represents a P+ layer, reference numeral 203represents an N+ layer formed in the shape of a ring, reference numeral204 represents an insulating layer of SiO₂, reference numeral 205represents a P electrode, and reference numeral 206 represents an Nelectrode. The structure shown in FIG. 10 has the disadvantage that evencarriers 207 ascribable to long-wavelength light components which appearoutside the depletion layer 201 produce a photoelectric current withinthe diffusion length (Lp) of the carriers 207. In this way, inconventional light-receiving devices, reception of light having longerwavelengths than the desired wavelengths may cause a malfunction.

Light-receiving devices like this are usually used in a form coveredwith a visible light shielding resin to prevent malfunctions due tovisible light. Moreover, such light-receiving devices are extremelysusceptible to electromagnetic noise, and this also leads tomalfunctions in light-receiving modules incorporating them. To preventthis, a conductive film (metallized film) or the like is inserted in alight-receiving module, or a mesh-like structure is arranged in thelight-receiving window of a module case. On the other hand, in alight-receiving module sealed with a resin instead of being furnishedwith a metal case, a mesh-like metal conductive member is formed on thesurface of a light-receiving device incorporated therein.

In illumination apparatus employing an infrared light-receiving module,the effects of visible light are coped with by the use of alight-receiving module or light-receiving device covered with a visiblelight shielding resin. In reality, however, illumination apparatus arefitted with a band-path filter or the like to alleviate the effects oflight from a fluorescent lamp which contains light components at manywavelengths spread across its spectrum. Moreover, in recent years, as itbecomes increasingly common to use a plurality of fluorescent lampstogether or to use fluorescent lamps with increasingly high outputs,more attention than ever has come to be paid to malfunctions oflight-receiving modules ascribable to light components at particularwavelengths (for example, at 1,013 nm) within the spectrum of the lightfrom a fluorescent lamp. For these reasons, light-receiving modules inpractical use either have an interference filter arranged on top of alight-receiving device covered with a visible light shielding resin soas to receive signals cleared of unwanted light components havingparticular wavelengths within the spectrum of the light present, or havean interference filter embedded in a visible light shielding resin.

This increases the number of components and the number of assembly stepsrequired to fabricate light-receiving modules, and thus increases theircosts. Moreover, in a case where an interference filter is embedded in aresin, it is difficult to achieve satisfactory reliability in terms ofthe accuracy with which the interference filter is fitted, exfoliationof the resin from the interference filter, and other factors.

Moreover, in a light-receiving module sealed in a resin, a mesh-likemetal conductive member is formed on an internal light-receivingsurface, and forming such a conductive member directly on the surface ofa light-receiving device is equivalent to forming a parallel-platecapacitor there. This increases the capacitance of the device, and thusshortens the distance over which the light-receiving moduleincorporating it can receive signals.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a light-receivingdevice and a light-receiving module that do not malfunction even whenthey receive light having longer wavelengths than the desiredwavelengths. Another object of the present invention is to provide alight-receiving device and a light-receiving module that do notmalfunction even when they receive light having wavelengths other thanthose desired or the like, without an increase in the capacitance of thedevice. Another object of the present invention is to provide alight-receiving module that does not malfunction in response to unwantedlight having particular wavelengths or the like, without requiring aband-path filter, an interference filter, or a mesh-like structure in alight-receiving window.

To achieve the above objects, according to the present invention, in alight-receiving device having a high-concentration impurity layer of afirst conductivity type and a high-concentration impurity layer of asecond conductivity type formed on a substrate having a low impurityconcentration so as to function as a light-receiving portion, with thehigh-concentration impurity layers of the first and second conductivitytypes arranged in the same direction as the top surface of thesubstrate, a layer having a short carrier life time is formed on thebottom surface of the substrate. The layer having a short carrier lifetime may be a high-concentration impurity layer of the first or secondconductivity type. Alternatively, the layer having a short carrier lifetime may be a layer formed by adding to the substrate an impurity suchas gold that forms a deep level. One of the high-concentration impuritylayers of the first and second conductivity types may be shielded withan electrode that is kept at the identical potential with the other ofthe high-concentration impurity layers of the first and secondconductivity types. According to the present invention, alight-receiving module is fabricated by fixing a light-receiving deviceas described above on a lead frame with an insulating material.

Alternatively, according to the present invention, a light-receivingmodule is composed of a lead frame, a light-receiving device fixed onthe lead frame, and an insulating resin in which the lead frame and thelight-receiving device are integrally sealed. Here, the light-receivingdevice is composed of: a substrate having a low impurity concentration;a layer having a short carrier life time formed on the bottom surface ofthe substrate; a high-concentration impurity layer of a firstconductivity type formed on the top-surface side of the substrate so asto have a predetermined thickness; a high-concentration impurity layerof a second conductivity type formed on the top-surface side of thesubstrate so as to surround the high-concentration impurity layer of thefirst conductivity type, the high-concentration impurity layers of thefirst and second conductivity types together functioning as alight-receiving portion; an insulating layer formed on the top surfaceof the substrate; and an electrode formed on the insulating layer andkept at the identical potential with the high-concentration impuritylayer of the first conductivity type so as to shield thehigh-concentration layer of the second conductivity type. Moreover, thelayer having a short carrier life time is fixed on the lead frame withan insulating material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a light-receiving device embodyingthe invention.

FIG. 2 is a plan view of the light-receiving device of FIG. 1.

FIG. 3 is a plan view showing another light-receiving device embodyingthe invention.

FIG. 4 is a diagram showing spectral sensitivity characteristics.

FIG. 5 is a plan view showing a light-receiving module embodying theinvention.

FIG. 6 is a plan view showing another light-receiving device embodyingthe invention.

FIG. 7 is a sectional view of the light-receiving device of FIG. 6.

FIG. 8 is a schematic sectional view showing another light-receivingmodule embodying the invention.

FIG. 9 is a schematic sectional view showing a conventional example.

FIG. 10 is a schematic sectional view showing another conventionalexample.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. FIG. 1 is a sectional view showing thelight-receiving device of a first embodiment of the invention, and FIG.2 is a plan view thereof. The light-receiving device 1 has alight-receiving portion 3 formed on the top surface of a substrate 2having a low impurity concentration, and has a layer 4 having a shortcarrier life time formed on the bottom surface of the substrate 2.

The substrate 2 is formed out of, for example, a Si substrate of a firstconductivity type (P-type) having a device impurity concentration of4×10¹³ cm⁻³ or lower and a thickness of about 300 μm. This substrate 2is so prepared as to have a high resistance, for example a specificresistance of 500 Ωcm or higher, and functions as a (P−) layer 2 a. Inthe bottom surface of the substrate 2, an N-type impurity such asphosphorus (P) is diffused to form a high-concentration impurity layer 4of a second conductivity type (N-type) that functions as the layerhaving a short carrier life time and that has a depth (thickness) ofabout 150 μm. In the figure, for convenience sake, thishigh-concentration impurity layer 4 of the second conductivity type ismarked (N+B). The N-type high-concentration impurity layer 4 is soprepared as to have (when formed out of a Si substrate) an impurityconcentration higher than 1×10¹⁶ cm⁻³, at which the carrier life timestarts shortening sharply as the impurity concentration is increasedgradually when observed in a characteristic diagram (not shown) thatshows the carrier life time, taken along the vertical axis, with respectto the impurity concentration, taken along the horizontal axis; forexample, it is so prepared as to have an impurity concentration of about3×10¹⁸ cm⁻³.

The light-receiving portion 3 is composed of a high-density impuritylayer 30 of a first conductivity type and a high-concentration impuritylayer 31 of a second conductivity type that are arranged in the samedirection as the top surface of the substrate 2. In the figure, forconvenience sake, the high-density impurity layer 30 of the firstconductivity type is marked P+, and the high-density impurity layer 31of the second conductivity type is marked (N+F). The high-densityimpurity layer 30 of the first conductivity type is formed by diffusinga P-type impurity such as boron (B) in the shape of a ring in the topsurface of the substrate 2. This impurity layer 30 is so prepared as tohave an impurity concentration of about 3×10¹⁹ cm⁻³ and a depth of about3 μm. On the other hand, the high-density impurity layer 31 of thesecond conductivity type is formed by diffusing an N-type impurity suchas phosphorus (P) in a region surrounded by the layer 30 in the topsurface of the substrate 2. This layer 31 is so prepared as to have asheet resistance of about 20 Ω/□ and a depth (thickness) of 1 to 2 μm.

On the surface of the substrate 2, a film 5 of, for example, siliconoxide (SiO₂) is formed that functions as a surface-protection andanti-reflection film. Parts of the film 5 are removed byphotolithography to permit contact with the high-density impurity layers30 and 31 of the first and second conductivity types. On the film 5, ametal such as aluminum is vapor-deposited and the unnecessary portionthereof is removed by photolithography to form a P-side and an N-sideelectrode 6 and 7.

Now, the operation of the light-receiving device of this embodiment willbe described, with the focus placed on how it cuts long-wavelength lightcomponents. First, the quantum efficiency R with which the lightincident on the light-receiving device 1 is converted into aphotoelectric current in the depth direction is given byR=1−exp(−αW)/(1+αLp). Here, W represents the thickness of thelow-concentration impurity region 2 a (i.e., the thickness of thedepletion layer that expands on application of a reverse voltage), arepresents the optical absorption coefficient for light having a givenwavelength, and Lp represents the diffusion length of carriers in thehigh-concentration impurity layer 4 on the bottom surface. Accordingly,the efficiency R can be increased by giving the low-concentrationimpurity region 2 a a sufficient thickness W, in other words, byrestricting the thickness W for unwanted light components havingparticular wavelengths. However, in the light-receiving device shown inFIG. 9 and described earlier, even when the thickness W of thelow-concentration region 101 is restricted, of the carriers generated inthe high-concentration impurity layer 107, those ascribable to thediffusion length Lp produce a photoelectric current, and this makes itimpossible to sufficiently reduce long-wavelength light components. Onthe other hand, in the light-receiving portion formed on the top surfaceof the light-receiving device shown in FIG. 10, since an electric fieldis applied parallel to the top surface of the substrate, the expansionof the depletion layer 201, which is the region in which light can bereceived efficiently, in the depth direction can be reduced, but, of thecarriers that are produced outside the depletion layer, those ascribableto the diffusion length Lp produce a photoelectric current, and thismakes it impossible to sufficiently reduce long-wavelength lightcomponents.

By contrast, in the first embodiment of the invention, as shown in FIGS.1 and 2, the high-concentration impurity layer 4 formed on the backsurface of the low-concentration impurity region 2 a serves to restrictthe thickness of the latter to the thickness W calculated according tothe formula noted above. This makes it possible to eliminate thecarriers generated in the high-concentration impurity layer 4 quicklybefore they produce a photoelectric current. Here, thehigh-concentration impurity layer on the back surface is independent ofthe electrodes (P-side and N-side electrodes 6 and 7) on the top surfaceso as to be electrically insulated therefrom.

In this way, the high-concentration impurity layer 4 restricts thethickness W of the low-concentration impurity region 2 a (depletionlayer) to the optimum thickness, and in addition shortens the life timeof the carriers generated by unnecessary light components that havereached the high-concentration impurity layer 4 (i.e., shortens Lp) soas to prevent their diffusion. Thus, it is possible to sufficiently cutunwanted light components (long-wavelength light components).

In this embodiment, to eliminate incident light having a wavelength of1,000 nm, the P-type low-concentration impurity region 2 a is given athickness W of 90 μm. Here, the high-concentration impurity layer 4 onthe back surface has a carrier diffusion length of 1 μm and an opticalabsorption coefficient of 7×10¹ cm⁻¹ for incident light having awavelength of 1,000 nm. FIG. 4 shows the spectral sensitivitycharacteristic A of the light-receiving device shown in FIG. 1 and thespectral sensitivity characteristic B of the light-receiving deviceshown in FIG. 9. This figure shows that the light reception sensitivityfor incident light having a wavelength of 1,000 nm here is reduced toabout one sixth of that obtained conventionally.

FIG. 3 shows a modified embodiment of the light-receiving device 1. Thislight-receiving device has the same internal structure as the one shownin FIG. 1 and described above, but has a different surface shapetherefrom. Specifically, here, the high-density impurity layer 30 asseen in a plan view is so shaped as to surround the high-densityimpurity layer 31 from three sides, instead of from four sides.Moreover, the P-side and N-side electrodes 6 and 7 are arranged inopposite parts of the light-receiving device, instead of side by side.

FIG. 5 is a plan view of a principal portion of a light-receiving module8 embodying the invention which incorporates the light-receiving device1. This light-receiving module 8 has the light-receiving device 1mounted on a metal lead frame 9, and has these integrally sealed in amolding of an insulating resin 10 containing an ingredient that shieldsvisible light. Here, the light-receiving device 1 is mounted, withconductive adhesive, on a central lead frame portion 12, which isseparated from other lead frame portions 13 and 14, so that thelight-receiving device 1 is electrically insulated therefrom. Betweenthe two side lead frame portions 13 and 14 and the P-side and N-sideelectrodes 6 and 7, gold wires 15 a and 15 b or the like are laid bywire bonding to permit extraction of a detection signal from thelight-receiving device 1.

FIGS. 6 and 7 show still another embodiment of the light-receivingdevice 1, where an electromagnetic shield is provided on thelight-receiving surface. FIG. 7 is a sectional view along line A—A shownin FIG. 6. This light-receiving device 1 has a structure similar to thatof the light-receiving device shown in FIG. 1, but differs therefrom inthat the conductivity types of the substrate 2 and the light-receivingportion 3 are completely opposite in terms of whether their materialsare of an N- or P-type, that an electrode 16 for shielding is formed onthe surface of the substrate 2, and other aspects. Specifically, thesubstrate 2 having a low impurity concentration is formed out of, forexample, an N-type Si substrate having a device impurity concentrationof 4×10¹³ cm⁻³ or lower and a thickness of about 300 μm. The layer 4having a short carrier life time formed on the back surface of thesubstrate 2 is formed as a high-concentration impurity layer of the sameconductivity type as the substrate 2, i.e., N-type. This N-typehigh-concentration impurity layer 4 is so prepared as to have, forexample, an impurity concentration of about 3×10¹⁸ cm⁻³ and a depth(thickness) of 150 μm.

The light-receiving portion 3 is composed of a high-density impuritylayer 32 of a first conductivity type and a high-concentration impuritylayer 33 of a second conductivity type that are arranged in the samedirection as the top surface of the substrate 2. In the figure, forconvenience' sake, the high-density impurity layer 32 of the firstconductivity type is marked P+, and the high-density impurity layer 33of the second conductivity type is marked (N+F). The high-densityimpurity layer 32 of the first conductivity type is formed by diffusinga P-type impurity such as boron (B) in a central portion of the topsurface of the substrate 2. This impurity layer 32 is so prepared as tohave a sheet resistance of about 20 Ω/□ and a depth of 1 to 2 μm. On theother hand, the high-density impurity layer 33 of the secondconductivity type is formed by diffusing an N-type impurity such asphosphorus in the top surface of the substrate 2 so as to surround theregion in which the layer 30 is formed. This layer 31 is so prepared asto have an impurity concentration of about 3×10¹⁹ cm⁻³ and a depth(thickness) of about 3 μm.

On the surface of the substrate 2, an insulating film 5 of, for example,silicon oxide (SiO₂) is formed that functions as a surface-protectionand anti-reflection film. Parts of the film 5 are removed byphotolithography to permit contact with the high-density impurity layers32 and 33 of the first and second conductivity types. On the film 5, ametal such as aluminum is vapor-deposited and the unnecessary portionthereof is removed by photolithography to form a P-side and an N-sideelectrode 60 and 70. The N-side electrode 70 formed on the insulatingfilm 5 is so formed as to be wider than the layer 33. The P-sideelectrode 60 is formed in the shape of a ring so as to cover the layer33 completely from above except in the region thereof where the N-sideelectrode 70 is formed, and thus forms the electrode 16 for shielding.

FIG. 8 shows a light-receiving module 8 embodying the invention whichincorporates the light-receiving device 1 shown in FIGS. 6 and 7. Thislight-receiving module 8 has the light-receiving device 1 and an IC 17for driving it mounted on a common lead frame 9, and has theseintegrally sealed in a molding of a resin 10, forming a single-moldingstructure. The resin 10 used here is an insulating resin containing amaterial that shields visible light, but the molding may be formed outof a resin of another type.

In general, a monolithic structure having a light detector and a driverIC formed on a single chip suffers from insufficient light receptionsensitivity of the light detector. For this reason, this light-receivingmodule 8 adopts a two-chip structure that combines together alight-receiving device and a driver IC 17 that excel in high operatingspeed and high sensitivity. Specifically, on the lead frame 9, thelight-receiving device 1 is fixed with insulating adhesive 18, and theIC 17 is fixed with conductive adhesive 19. Thus, the only additionalconnection needed between the light-receiving device 1 and the IC 17 isthe wiring between the N-side electrode 70 of the former and anamplifier circuit portion of the latter with a gold wire 20 or the like.The P-side electrode 60 of the light-receiving device 1 is wired to thelead frame 9 with a gold wire 21 or the like so as to be connected tothe ground potential.

As described above, by bonding the light-receiving device 1 on thecommon lead frame 9 with the insulating adhesive 18 and then connectingto the lead frame 9 with the wire 21 the electrode 60 that connects tothe layer 32, which is the light-receiving surface formed on the topsurface of the light-receiving device 1, it is possible to realize astructure in which the light-receiving device 1, which is susceptible toelectromagnetic noise, is sandwiched between identical potentials fromabove and below, and thereby achieve effective electromagneticshielding. Moreover, the surface of the layer 33 can also be shieldedwith the shielding electrode 16.

For more effective electromagnetic shielding, the light-receiving moduleshown in FIG. 8 is provided with a structure that permits the sidesurfaces of the light-receiving device 1 to be covered with a potentialidentical with that of the lead frame 9. Specifically, walls 22 havingabout the same height as the side surfaces of the light-receiving device1 are formed integrally with the lead frame 9, and these walls 22 alsoare used for electromagnetic shielding. Alternatively, a portion of thelead frame 9 may be formed into a depressed portion so that thelight-receiving device 1 is housed inside it. Even a single such wall 22covering a side surface of the light-receiving device 1 contributes toelectromagnetic shielding, but it is preferable to provide a pluralityof such walls to cover more, further preferably all the four, sidesurfaces of the light-receiving device 1. These walls 22 are notabsolutely necessary in structural terms, but are useful to achieve agreater shielding effect.

The embodiments described above deal with, as examples, light-receivingdevices 1 of a PIN photodiode type. However, the present inventionapplies not only to light-receiving devices of this particular type butalso to common photodiodes of a PN type and to light-receiving devicesintegrated in ICs formed on the same substrates as driver ICs.

The embodiments described above deal with examples in which an N-typehigh-concentration impurity layer is used as a layer 4 having a shortcarrier life time. However, it is also possible to use a P-typehigh-concentration impurity layer instead. A layer formed by adding tothe substrate an impurity such as gold that forms a deep level alsohelps shorten the carrier life time, and therefore it is also possibleto use such a layer as the layer 4. The embodiments described aboveoffer the following advantages.

(1) It is possible to give the light-receiving device itself thefunction of a cut filter, i.e., that of reducing the sensitivity tolong-wavelength light. Conventionally, illumination apparatus are fittedwith a band-path filter or the like to alleviate the effects of lightfrom a fluorescent lamp which contains light components at manywavelengths spread across its spectrum. Moreover, in recent years, as itbecomes increasingly common to use a plurality of fluorescent lampstogether or to use fluorescent lamps with increasingly high outputs,more attention than ever has come to be paid to malfunctions oflight-receiving modules ascribable to light components at particularwavelengths (for example, at 1,013 nm) within the spectrum of the lightfrom a fluorescent lamp. For these reasons, light-receiving modules inpractical use either have an interference filter arranged on top of alight-receiving device covered with a visible light shielding resin soas to receive signals cleared of unwanted light components havingparticular wavelengths within the spectrum of the light present, or havean interference filter embedded in a visible light shielding resin. Thisincreases the number of components and the number of assembly stepsrequired to fabricate light-receiving modules, and thus increases theircosts and imposes restrictions on their sizes. All these problems can beovercome, and thus it is possible to realize inexpensive, ultra-compactlight-receiving modules.

(2) In a case where an interference filter is embedded in a resin, it isdifficult to achieve satisfactory reliability in terms of the accuracywith which the interference filter is fitted, exfoliation of the resinfrom the interference filter, and other factors. Such instability can beprecluded. Moreover, it is possible to prevent generation of carriers ata junction (i.e., outside a depletion layer), and thereby suppressdiffusing carriers, while leaving drifting carriers alone, so as toachieve fast response.

(3) The light-receiving device itself is given, on the top and sidesurfaces thereof, the function of electromagnetic shielding. When ametal conductive member is used as an electromagnetic shield, incidentlight is reflected by the metal conductive member, which thus reducesthe effective light reception area (a loss of incident light). This canbe overcome. Using a metal conductive member as an electromagneticshield reduces the effective light reception area, and therefore themetal conductive member cannot be arranged over an unduly large area onthe surface of the light-receiving device. This results in insufficientelectromagnetic shielding. By contrast, in the embodiments describedabove, the surface of the light-receiving device serves, on its own, asa shielding layer, offering sufficient electromagnetic shielding. In alight-receiving module sealed in a resin, a mesh-like metal conductivemember is formed on an internal light-receiving surface, and formingsuch a conductive member directly on the surface of a light-receivingdevice is equivalent to forming a parallel-plate capacitor there. Thisincreases the capacitance of the device, and thus shortens the distanceover which the light-receiving module incorporating it can receivesignals. By contrast, in the embodiments described above, it is possibleto prevent an increase in the capacitance of the device, and therebyavoid shortening the distance over which the light-receiving moduleincorporating it can receive signals. Since the light-receiving deviceitself is given the function of electromagnetic shielding, there is noneed to provide a conductive film (metallized film) as conventionallyfitted inside a light-receiving module against electromagnetic noise, oreven a mesh-like structure as conventionally arranged in thelight-receiving window of a module case. In this way, it is possible toeliminate separate components for electromagnetic shielding, and thus torealize a super-compact light-receiving module. In the embodimentsdescribed above, separate components for electromagnetic shielding maybe used together, in which case it is possible to achieve a much greaterelectromagnetic shielding effect than with conventional structures,although there is a limit to miniaturization.

(4) Another advantage is that, as in the embodiment shown in FIGS. 6 and7, by covering the layer 33 connected to one electrode 70 (the electrodefrom which a signal is extracted) with the other electrode 60 (theelectrode connected to a predetermined potential), it is possible tomake changes, as necessary, in the shapes of the electrodes and in thearrangement of the P-type and N-type layers of the device.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto minimize the effects of noise and thereby prevent malfunctions. It ispossible to reduce the number of components and the number of assemblysteps. It is possible to prevent an increase in the capacitance of adevice and thereby achieve fast response. It is possible to achieveminiaturization. In this way, the present invention is desirable interms of performance, design, fabrication, and costs, and thus findswide application in light-receiving devices and light-receiving modulessuch as infrared remote control devices.

1. A light-receiving device comprising: a substrate having alow-concentration impurity region; a high-concentration impurity layerof a first conductivity type and a high-concentration impurity layer ofa second conductivity type, one of which serves as an anode and theother serves as a cathode of the light-receiving device, each having apredetermined thickness, and formed at a light-entering side of thesubstrate and in contact with the low-concentration impurity region soas to function as a light-receiving portion; and a layer having a shortcarrier life time, formed in contact with the low-concentration impurityregion at a bottom surface of the substrate so as to restrict adepletion layer in the low-concentration impurity region of thesubstrate to a predetermined thickness and eliminate carriers generatedwithin the layer quickly before the carriers produce a photoelectriccurrent.
 2. A light-receiving device as claimed in claim 1 wherein thelayer having a short carrier life time is a high-concentration impuritylayer of the first or second conductivity type.
 3. A light-receivingdevice as claimed in claim 1 wherein the layer having a short carrierlife time is a layer formed by adding to the substrate an impurity suchas gold that forms a deep level.
 4. A light-receiving device as claimedin claim 1 wherein one of the high-concentration impurity layers of thefirst and second conductivity types is shielded with an electrode thatis kept at an identical potential with the other of thehigh-concentration impurity layers of the first and second conductivitytypes.
 5. A light-receiving device comprising: a substrate having a lowimpurity concentration; a layer having a short carrier life time formedon a bottom surface of the substrate; a high-concentration impuritylayer of a first conductivity type formed on a top-surface side of thesubstrate so as to have a predetermined thickness; a high-concentrationimpurity layer of a second conductivity type formed on the top-surfaceside of the substrate so as to surround the high-concentration impuritylayer of the first conductivity type, the high-concentration impuritylayers of the first and second conductivity types together functioningas a light-receiving portion; an insulating layer formed on a topsurface of the substrate; and an electrode formed on the insulatinglayer and kept at an identical potential with the high-concentrationimpurity layer of the first conductivity type so as to shield thehigh-concentration layer of the second conductivity type.
 6. Alight-receiving device as claimed in claim 5, wherein the electrode iswider than the high-concentration impurity layer of the secondconductivity type, and is formed parallel to the high-concentrationimpurity layer of the second conductivity type with the insulating layersandwiched in between.
 7. A light-receiving module comprising a leadframe, a light-receiving device fixed on the lead frame, and aninsulating resin in which the lead frame and the light-receiving deviceare integrally sealed, wherein the light-receiving device comprises: asubstrate having a low impurity concentration; a layer having a shortcarrier life time formed on a bottom surface of the substrate; ahigh-concentration impurity layer of a first conductivity type formed ona top-surface side of the substrate so as to have a predeterminedthickness; a high-concentration impurity layer of a second conductivitytype formed on the top-surface side of the substrate so as to surroundthe high-concentration impurity layer of the first conductivity type,the high-concentration impurity layers of the first and secondconductivity types together functioning as a light-receiving portion; aninsulating layer formed on a top surface of the substrate; and anelectrode formed on the insulating layer and kept: at an identicalpotential with the high-concentration impurity layer of the firstconductivity type so as to shield the high-concentration layer of thesecond conductivity type, and the layer having a short carrier life timeis fixed on the lead frame with an insulating material.
 8. Alight-receiving module as claimed in claim 7, wherein the layer having ashort carrier life time is connected to the lead frame.
 9. Alight-receiving module comprising a lead frame and a light-receivingdevice fixed on the lead frame, wherein the light-receiving devicecomprises: a substrate having a low impurity concentration; ahigh-concentration impurity layer of a first conductivity type and ahigh-concentration impurity layer of a second conductivity type, eachhaving a predetermined thickness and formed at a light entering side ofthe substrate so as to function as a light-receiving portion; and alayer having a short carrier life time, formed in contact with a bottomsurface of the substrate so as to restrict a thickness of the substrateand eliminate carriers generated within the layer quickly before thecarriers produce a photoelectric current, and wherein the layer having ashort carrier life time is fixed on the lead frame with an insulatingmaterial.